我目前正在研究涉及畫布元素的項目,並在調整畫布大小時遇到問題。我試圖通過將寬度和高度除以2來在畫布中心繪製圖像,但是每當我調整畫布大小時,它只會更改HTML,因此當我重新繪製圖像時,仍然會畫一半舊畫布的寬度和高度。我不確定這是否是一個DOM問題或什麼,但將不勝感激任何幫助。代碼HTML5畫布僅調整大小html
<body>
<div id="holder">
<div id="dropdown">
<div id="ddcontents" style="display: none;">
<button onclick="fade()">Options</button>
<button onclick="getSize()">Canvas Size</button>
<button onclick="redraw()" disabled="true">Redraw</button>
</div>
</div>
<canvas id="c" height="480" width="640">Your browser does not support HTML5.</canvas>
<div id="options" style="display: none">
<div id="optcontent" style="display: none">
<center><h1>Options</h1></center>
<div id="sound">
<div>Volume:
<form oninput="volumenumber.value = parseInt(volume.value)">
<input type="range" name="volume" min="0" max="100" value="80" disabled="true">
<input type="hidden" name="hello" value="%">
<output name="volumenumber" for="volume">80</output>
</form>
Resolution:
<select id="resolution">
<option value="480p">480x640</option>
<option value="720p">720x1280</option>
</select>
</div>
</div>
<div id="closeoptions">
<button onclick="apply()">Apply</button>
</div>
</div>
</div>
</div>
<script src="options.js"></script>
</body>
</html>
而對於JS:我在Safari瀏覽器,FF和Chrome
編輯測試
var c = document.getElementById('c');
var ctx=c.getContext("2d");
var img=new Image();
var w = this.c.clientWidth; // stores the width for later use
var h = this.c.clientHeight;
this.c.width = w;
this.c.height = h;
var cwidth = c.width;
var cheight = c.height;
img.onload = function(){
ctx.drawImage(img,w/2 - 14,h/2 - 19);
};
img.src="image_preview.png";
function apply()
{
var reso = document.getElementById("resolution");
var resol = reso.options[reso.selectedIndex].value;
//alert(resol)
if (resol == "720p")
{
//alert("You changed to 720p");
h = 720;
w = 1280;
cheight = 720;
cwidth = 1280;
}
else if (resol == "480p")
{
//alert("You changed to 480p");
h = 480;
w = 640;
cheight = 480;
cheight = 640;
}
getSize();
redraw();
}
function redraw()
{
ctx.drawImage(img,w/2 - 14,h/2 - 19);
img.src="image_preview.png";
}
function getSize()
{
alert(h + "x" + w);
}
如果你可以在jsfiddle.net或jsbin.com上發佈你的代碼來展示問題,它會讓某人更容易確定什麼是錯誤的。 – 2012-08-17 18:05:48
發表,與dystroy的編輯。 – 2012-08-17 18:37:18